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NF-κB/RelA signaling required for CD40-induced humoral immunity depends on specific NEMO lysine residues in mice
Donna Li1, Shelly M Wuerzberger-Davis1, Yuhong Chen2
1McArdle Laboratory for Cancer Research, Department of Oncology, Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI, USA.
Abstract:
Oxidative stress and genotoxic damage activate NF-κB signaling through intracellular pathways distinct from those initiated by membrane receptors. DNA damage selectively induces post-translational modifications at lysine residues 277 and 309 of the human ubiquitin-binding protein NEMO to promote NF-κB signaling, but the physiological importance of these modifications in vivo remains unclear. Here, we show that a newly developed mouse model (NEMODK) carrying germline arginine substitutions of the corresponding NEMO lysine residues exhibits B-cell-intrinsic defects in germinal center formation and anti-viral humoral responses. Mechanistically, we identify in NEMODK B-cells a CD40-specific NF-κB signaling defect that is not linked to the well-characterized canonical or noncanonical NF-κB pathways. These B-cells fail to secure sustained NEMO monoubiquitination following CD40-induced ROS generation, which specifically reduces downstream RelA (p65) signaling required for the transcriptomic and epigenetic remodeling underlying homotypic B-cell aggregation, cell proliferation, class-switch recombination, and antibody-secreting cell generation. Our results establish a physiological role of murine NEMO K270 and K302 in linking CD40 engagement to B-cell responses through enabling sustained NEMO modification and RelA transcriptional activity.
Insights
Newly identified mouse model NEMODK reveals critical roles for NEMO protein modifications in B-cell immune responses. These findings highlight a novel pathway linking CD40 signaling to NF-κB activation and B-cell function.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Oxidative stress and DNA damage activate NF-κB signaling via distinct intracellular pathways.
- Specific post-translational modifications of the ubiquitin-binding protein NEMO (human K277/K309) are implicated in NF-κB activation, but their in vivo significance is unknown.
Purpose of the Study:
- To investigate the physiological importance of NEMO lysine modifications in vivo.
- To elucidate the role of these modifications in B-cell immune responses and NF-κB signaling.
Main Methods:
- Development of a novel mouse model (NEMODK) with germline arginine substitutions at key NEMO lysine residues.
- Analysis of B-cell intrinsic defects in germinal center formation and anti-viral humoral responses.
- Investigation of CD40-specific NF-κB signaling defects and NEMO monoubiquitination in NEMODK B-cells.
Main Results:
- NEMODK mice exhibit B-cell-intrinsic defects in germinal center formation and anti-viral humoral responses.
- NEMODK B-cells display a CD40-specific NF-κB signaling defect, independent of canonical/noncanonical pathways.
- These B-cells fail to sustain NEMO monoubiquitination after CD40 stimulation, impairing downstream RelA (p65) signaling.
Conclusions:
- Murine NEMO K270 and K302 are crucial for linking CD40 engagement to B-cell responses.
- Sustained NEMO modification and RelA transcriptional activity are essential for B-cell proliferation, class-switch recombination, and antibody production.
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